Potential impact of joint association of alanine aminotransferase and gamma-glutamyltransferase on insulin resistance in Japan: The Toranomon Hospital Health Management Center Study 19 (TOPICS 19).

AIM:To investigate the potential impact of joint association of alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT) on insulin resistance and β-cell dysfunction in healthy Japanese individuals with a normal range of liver enzymes. METHODS:This study included 1010 individuals (545 men and 465 women) aged 20-89 years who underwent an oral glucose tolerance test for health screening. Participants were divided into four groups on the basis of median values for ALT and GGT: (i) both ALT and GGT low (both-low); (ii) ALT high and GGT low (ALT-high); (iii) ALT low and GGT high (GGT-high); and (iv) both ALT and GGT high (both-high). Logistic regression analysis was used to investigate the relationship between liver enzyme and insulin dynamics, such as Homeostasis Model of Assessment - Insulin Resistance (HOMA-IR) and insulinogenic index (IGI). The insulin resistance was defined when HOMA-IR was 2.5 or more. IGI of less than 0.4 was considered to be decreased early-phase insulin secretion. RESULTS:Mean values of HOMA-IR in men was 1.5 in the both-low group, 1.8 in ALT-high, 1.8 in GGT-high and 2.8 in both-high. The mean HOMA-IR in women was 1.3 in the both-low group, 1.3 in ALT-high, 1.6 in GGT-high and 2.0 in both-high. HOMA-IR in the both-high group was significantly higher than that in the both-low group regardless of the difference of sex. Multivariate analysis showed that insulin resistance occurred when the patient had high liver enzymes. CONCLUSION:Combining the two liver function markers would be effective for identifying individuals with insulin resistance.